My two cents is if you are doing the full IBDP, you do not have to worry about having enough rigor!
So in addition to that, just take the elective class you want to take.
Oh, and there are very few college at which your school-weighted GPA is actually relevant for admissions or merit. There is a thread which is collecting them:
But it isn’t many. So I would personally not worry at all about that issue.